The present invention is directed to a rectangular flexible duct, and more particularly to a heating and ventilating duct which is collapsible and rollable.
Heating and ventilating ducts, especially for home use, are at the present time constructed of rectangular rigid sheet metal or fiberglass, or in the form of a flexible plastic tube which has a continuous spiral of wire within it. In any case, it is expensive, bulky, difficult to transport, requires a large storage space and requires pre-sizing.
Flexible and foldable, and in fact, rollable air flow conduits have been suggested, as shown in Kice Patent No. 2,821,896 and Hedges Patent No. 3,818,948. Kice shows a fiberglass duct which is collapsible on its four corners and rollable and has a very specific use for a wall space. All the walls of the rectangular duct are of the same fiberglass material. It is not rigid enough nor usable under flooring for general home heating and ventilating use. It is also difficult to roll.
The Hedges patent again shows a rectangular duct which is collapsible at its four corners. However, because of its stiffening arrangement (although it is somewhat bendable), it is not rollable.
Thus, as is apparent from the above prior art, attempts have been made to remedy the deficiencies of, for example, rigid sheet metal ducts, but they have not been totally successful.